scholarly journals Population assessment of tropical tuna based on their associative behavior around floating objects

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Capello ◽  
J. L. Deneubourg ◽  
M. Robert ◽  
K. N. Holland ◽  
K. M. Schaefer ◽  
...  
Keyword(s):  
Population Assessment ◽  
Associative Behavior ◽  
Tropical Tuna ◽  
Floating Objects

scholarly journals Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries

2020 ◽  
Author(s):  
Gwenaëlle Wain ◽  
Loreleï Guéry ◽  
David Michael Kaplan ◽  
Daniel Gaertner
Keyword(s):  
New Technology ◽  
Recent Change ◽  
Purse Seine ◽  
Catch Per Unit Effort ◽  
Katsuwonus Pelamis ◽  
Thunnus Obesus ◽  
Efficiency Increase ◽  
Tropical Tuna ◽  
Floating Objects ◽  
The Impact

Abstract Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (≈10%) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase.

Fishing on floating objects (FOBs): how French tropical tuna purse seiners split fishing effort between GPS-monitored and unmonitored FOBs

2018 ◽  
Vol 75 (11) ◽  
pp. 1849-1858 ◽  
Author(s):  
Julia E. Snouck-Hurgronje ◽  
David M. Kaplan ◽  
Emmanuel Chassot ◽  
Alexandra Maufroy ◽  
Daniel Gaertner
Keyword(s):  
Search Time ◽  
Fishing Effort ◽  
Purse Seine ◽  
Trajectory Data ◽  
Catch Per Unit Effort ◽  
Position Information ◽  
Foreign Objects ◽  
Tropical Tuna ◽  
Floating Objects ◽  
Over Time

Fishing on floating objects (FOBs) dominates catch in tropical tuna purse seine fisheries. One frequently cited advantage of deploying GPS-monitored FOBs is that the position information can be used for directed fishing to reduce search time for tuna. However, purse seiners also fish on foreign objects for which position information is not available. It is critical to quantify the prevalence of fishing on GPS-monitored versus unmonitored FOBs to understand how they impact fishing effort and catch per unit effort. We analyzed French commercial, observer, and FOB trajectory data in the Atlantic and Indian oceans to determine how often purse seine vessels fish on GPS-monitored FOBs. Only 2.7%–20.4% of French FOB fishing sets over 2007–2013 in both oceans were made on GPS-monitored FOBs. Though increasing over time, the low percentage suggests that French vessels do not primarily use GPS-monitored FOBs to reduce search time for tuna. We hypothesize that fishery-wide FOB deployments have important collective consequences for overall fishing effort and recommend that future effort metrics should be based on fishery-wide FOB activities.

Article

1999 ◽  
Vol 56 (6) ◽  
pp. 984-993 ◽  
Author(s):  
Laurent Dagorn ◽  
Pierre Fréon
Keyword(s):  
School Size ◽  
Temporal Dynamics ◽  
Fusion Rule ◽  
After School ◽  
Dynamic Approach ◽  
Free Swimming ◽  
Individual Based Models ◽  
Tropical Tuna ◽  
Floating Objects ◽  
School Cohesion

Among the different assumptions proposed to explain why tropical tuna aggregate around floating objects ("logs"), one of the most recent is that floating objects may represent meeting points for tuna. This "meeting point hypothesis" proposes that tuna can use these floating objects to form larger schools after school fission or dispersion. The influence of meeting points on tuna school sizes is explored through different individual-based models that consider a single fusion rule and a variety of fission rules based on energetic considerations, the role of school size on school cohesion, predator attacks, and dispersion during the night. Results are first analyzed using an averaging approach to study the overall mean school size in habitats having different floating object densities. Second, a dynamic approach is used to compare the temporal dynamics of associated and free-swimming school sizes. The averaging approach indicates that in all the models (except those based on energetics), floating objects increase school size, at least up to a certain object density. The dynamic approach clearly illustrates different dynamics in the school size of associated and free-swimming schools. Most of our models show that tuna associated with logs resume schooling in larger schools after fission events.

Surface habitat modification through industrial tuna fishery practices

2021 ◽  
Author(s):  
Amaël Dupaix ◽  
Manuela Capello ◽  
Christophe Lett ◽  
Marco Andrello ◽  
Nicolas Barrier ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Indian Ocean ◽  
Habitat Modification ◽  
Pelagic Species ◽  
The Indian Ocean ◽  
Tropical Tuna ◽  
Associated Species ◽  
Floating Objects ◽  
Fish Aggregating Devices ◽  
Tuna Fishery

Abstract Natural floating objects (FOBs) have always been a major component of the habitat of pelagic species. Since the 1990s, the number of FOBs in the open ocean has increased greatly as a result of the introduction of fish aggregating devices (FADs) by the industrial tropical tuna purse seine vessels. These changes, and their potential impacts on the species that associate with FOBs, remain poorly understood. Using fisheries observer data, data from satellite-linked tracking buoys attached to FOBs and Lagrangian simulations, this study quantifies the temporal changes in the density and spatial distribution of FOBs due to the use of FADs in the Indian Ocean (IO) between 2006 and 2018. From 2012 to 2018, the entire western IO is impacted, with FADs representing more than 85% of the overall FOBs, natural FOBs less than 10%, and objects originating from pollution 5%. Results also suggest that both FADs and natural FOBs densities are lower in the eastern IO, but this initial investigation highlights the need for further studies. Our study confirms that FADs have greatly modified the density and spatial distribution of FOBs, which highlights the need to investigate potential consequences on the ecology of associated species.

Massive increase in the use of drifting Fish Aggregating Devices (dFADs) by tropical tuna purse seine fisheries in the Atlantic and Indian oceans

2016 ◽  
Vol 74 (1) ◽  
pp. 215-225 ◽  
Author(s):  
Alexandra Maufroy ◽  
David M. Kaplan ◽  
Nicolas Bez ◽  
Alicia Delgado De Molina ◽  
Hilario Murua ◽  
...  
Keyword(s):  
Relative Proportion ◽  
Major Change ◽  
Purse Seine ◽  
Fourfold Increase ◽  
Natural Objects ◽  
The Indian Ocean ◽  
Tropical Tuna ◽  
Floating Objects ◽  
Fish Aggregating Devices ◽  
Logbook Data

Since the mid-1990s, drifting Fish Aggregating Devices (dFADs), artificial floating objects designed to aggregate fish, have become an important mean by which purse seine fleets catch tropical tunas. Mass deployment of dFADs, as well as the massive use of GPS buoys to track dFADs and natural floating objects, has raised serious concerns for the state of tropical tuna stocks and ecosystem functioning. Here, we combine tracks from a large proportion of the French GPS buoys from the Indian and Atlantic oceans with data from observers aboard French and Spanish purse seiners and French logbook data to estimate the total number of dFADs and GPS buoys used within the main fishing grounds of these two oceans over the period 2007–2013. In the Atlantic Ocean, the total number of dFADs increased from 1175 dFADs active in January 2007 to 8575 dFADs in August 2013. In the Indian Ocean, this number increased from 2250 dFADs in October 2007 to 10 300 dFADs in September 2013. In both oceans, at least a fourfold increase in the number of dFADs was observed over the 7-year study period. Though the relative proportion of natural to artificial floating objects varied over space, with some areas such as the Mozambique Channel and areas adjacent to the mouths of the Niger and Congo rivers being characterized by a relatively high percentage of natural objects, in no region do dFADs represent <50% of the floating objects and the proportion of natural objects has dropped over time as dFAD deployments have increased. Globally, this increased dFAD use represents a major change to the pelagic ecosystem that needs to be closely followed in order to assess its impacts and avoid negative ecosystem consequences.

Dynamics of floating objects at high particulate Reynolds numbers

2020 ◽  
Vol 5 (5) ◽  
Author(s):  
H. Ghaffarian ◽  
D. Lopez ◽  
E. Mignot ◽  
H. Piegay ◽  
N. Riviere
Keyword(s):  
Reynolds Numbers ◽  
Floating Objects

scholarly journals Transitions in hookah (Waterpipe) smoking by U.S. sexual minority adults between 2013 and 2015: the population assessment of tobacco and health study wave 1 and wave 2

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mary Rezk-Hanna ◽  
Ian W. Holloway ◽  
Joy Toyama ◽  
Umme Shefa Warda ◽  
Lorree Catherine Berteau ◽  
...  
Keyword(s):  
Multinomial Logistic Regression ◽  
Health Study ◽  
Chi Square ◽  
Population Assessment ◽  
Logistic Regression Models ◽  
Global Epidemic ◽  
Product Use ◽  
Hookah Smoking ◽  
Nationally Representative ◽  
And Gender

Abstract Background Tobacco smoking using a hookah (i.e., waterpipe) is a global epidemic. While evidence suggests that sexual minorities (SM) have higher odds of hookah use compared to heterosexuals, little is known about their hookah use patterns and transitions. We sought to examine transitions between hookah smoking and use of other tobacco and electronic (e-) products among SM adults aged 18 years of age and older versus their heterosexual counterparts. Methods We analyzed nationally representative data of ever and current hookah smokers from Wave 1 (2013–2014; ever use n = 1014 SM and n = 9462 heterosexuals; current use n = 144 SM and n = 910 heterosexuals) and Wave 2 (2014–2015; ever use n = 901 SM and n = 8049 heterosexuals; current use n = 117 SM and n = 602 heterosexuals) of the Population Assessment of Tobacco and Health Study. Comparisons between groups and gender subgroups within SM identity groups were determined with Rao-Scott chi-square tests and multivariable survey-weighted multinomial logistic regression models were estimated for transition patterns and initiation of electronic product use in Wave 2. Results Ever and current hookah smoking among SM adults (ever use Wave 1: 29% and Wave 2: 31%; current use Wave 1: 4% and Wave 2: 3%) was higher than heterosexuals (ever use Wave 1: 16% and Wave 2: 16%; current use Wave 1: 1% and Wave 2: 1%; both p < 0.0001). Among SM adults who reported hookah use at Wave 1, 46% quit hookah use at Wave 2; 39% continued hookah use and did not transition to other products while 36% of heterosexual adults quit hookah use at Wave 2 and 36% continued hookah use and did not transition to other products. Compared with heterosexuals, SM adults reported higher use of hookah plus e-products (Wave 2 usage increased by 65 and 83%, respectively). Conclusions Compared to heterosexuals, in addition to higher rates of hookah smoking, higher percentages of SM adults transitioned to hookah plus e-product use between 2013 and 2015. Results have implications for stronger efforts to increase awareness of the harmful effects of hookah as well as vaping, specifically tailored among SM communities.

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